Differential pressure tool



Nov. 25, 1969 L, l.. cal-{ELF}` 3,480,088

DIFFERENTIAL PRESSURE TOOL Filed Dec. 1967 j/ j 7% Zi Wl f f ff Ma United States Patent O ABSTRACT OF THE DISCLOSURE A percussive tool which operates solely on a pressure differential, the tool having a piston with three sections of different cross-sectional area, the piston sections cooperating with the tool housing and elements suspended therein to provide a unique valving action which results in the driving of the piston, the tool further having a chuck characterized by the absence of threaded joints in the path of energy transfer between the piston and work.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to pneumatic tools. More particularly, the present invention is directed to the utilization of a pressure differential to drive a percussive type tool and to improvements in the manner of exhausting the drilling uid employed in and holding the work contacting portion of such tools. Accordingly, the general objects of the present invention are to provide new and improved methods and apparatus of such character.

Description of the prior art While not limited thereto in its utility, the present invention is particularly well suited for employment in down-hole percussive drilling tools. Such tools are well known in the art and are characterized by a uid operated piston which drives a drill, the piston and drill chuck housing Vbeing suspended at the bottom of a lrotatable tubing or drilling string. Prior art down-hole tools, while successful, have had certain inherent deliciencies.

One of the disadvantages of the prior art fluid actuated percussive tools is the fact that such tools have not made efficient use of available operating fluid. That is, due to the design of prior art down-hole percussive tools, the drilling fluid, generally compressed air, `was often wasted thus requiring excess compressor capacity to perform a given job.

As a second disadvantage, which is also primarily economic in character, prior art down-hole fluid percussive tools have, due to their complexity, been exceedingly expensive. The high cost of the prior art tools may be attributed to the design thereof which has required parts having inner and outer sliding surfaces of substantial length which must be carefully machined to tolerance. That is, the design of prior art tools required that concentricity and alignment be maintained between a precision machined inner shaft, a working piston and an outer housing in which the bore for the piston was machined to close tolerance.

A third deficiency of the prior art fluid actuated percussive tools of the down-hole type results from their susceptibility to failure in service. One of the major causes for tool failure has been metal fatigue in parts such as the compression spring which has typically been employed to drive the piston and/or hammer against the drilling tool after each spring compression cycle, the spring compression being produced by the action of the drilling uid on the piston.

M. 3,480,088 Ice Patented Nov. 25, 1969 Prior art drilling tools, particularly those of the downhole type have also been characterized by work holders or chucks which were relatively fragile and diflicult to manipulate. In the drilling of a well bore, it often happens that the drill will be broken and replacement thereof thus necessitated. In such instances, particularly in view of the substantial economic loss presented by drill rig down time, it is desired to change the tool as rapidly as possible. In the past, due to chuck design, drill changing has been a time consuming task.

One of the principal reasons for the aforementioned fragility of prior art chucks is that, as a means for tool insertion in the chuck, threaded joints were usually employed in the line of energy transfer between the piston and material being drilled. Threaded joints are to be preferred since their cost is considerably less than alternative approaches for mating the drill with the chuck. However, with the threaded joint in the energy transfer line, the chances of chuck or drill failure are greatly increased and the eiciency of the tool decreased due to energy losses in the threaded joint.

As is well known in the art, the length and weight of the chuck and drill of a down-hole percussive type tool should be equal to the length and weight of the piston which drives the drill. This requirement has somewhat restricted the design of the previously employed chucks to the use of such expedients as split halves which lock around splines. Use of split halves, however, further induces undue stresses in threaded joints between drill and chuck and, due to the space limitations imposed by the aforementioned design requirement, has limited the number of splines which could be incorporated into the chuck. This in turn, reduced the resistance to torque of the assembly. As a result, prior art chucks are quite susceptible to wear and breakage.

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned deficiencies of the prior art and in so doing provides a novel fluid operated, percussive type drilling tool suitable for down-hole use. The tool of the present invention comprises a unique, differential piston which, on both the down or energy delivery stroke and the up or return stroke, is operated solely by the drilling uid. This unique piston arrangement, which functions with the aid of only a single check valve, eliminates the need for compression springs, reduces precision machining requirements and Aresults in the more economic use of available drilling The present invention also comprises, in combination with the novel differential piston, a drill holding chuck which eliminates the split ring constructions of the prior art and which therefore employs more splines than are possible in prior art chucks. In addition, the present invention employs, as means for engaging the drill and chuck, a threaded joint which is outside of the line of energy transfer between the piston and work. The chuck of the present invention is thus less susceptible to failure in service and offers more resistance to torque than prior art devices of like character.

BRIEF DESCRIPTION OF THE DRAWING The present invention may be better understood and its numerous advantages will become apparent to those skilled in the art by reference to the accompanying drawing wherein like reference numerals refer to likel elements in the various figures and in which:

FIGURE 1 is a cross-sectional view of a preferred embodiment of the present invention showing the piston at the bottom of its down stroke.

FIGURE 2 is a partial, cross-sectional View of the tool of FIGURE 1 with the piston shown in its upper-most position of travel.

FIGURE 3 is a partial, cross-sectional view of the tool of FIGURE l showing the position assumed by the piston and tool when the drilling string is raised from the bottom of the bore.

FIGURE 4 is a cross-sectional View, taken along line 4 4 of FIGURE 1, showing the chuck of the tool of FIGURE 1.

FIGURE 5 is a cross-sectional view, taken along line 5 5 of FIGURE l, of the tool of FIGURE l.

FIGURE 6 is a cross-sectional view, taken along line 6 6 of FIGURE 1, of the piston of the tool of FIG- URE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGURE 1, the tool of the present invention comprises an outer housing 10 which defines a cylinder in which a differential piston, indicated generally at 12, moves. Housing 10 is attached at its upper end (the right-hand side of FIGURE 1), by a threaded connection 13, to a drilling string through which drilling fluid, usually compressed air, is supplied from a compressor. Mating of the tool to the drilling string is a-ccomplished by means of engaging flats on connector 16 with a Spanner Wrench. Compressed air enters housing 10 through the drilling string and center bore 14 of connector 16. At all times when the compressor is supplying drilling fluid under pressure to the tool, a spring loaded poppet type check valve, indicated generally at 18, will be open thereby allowing the drilling fluid to pass into the interior of housing 10.

The seat for valve 18 is defined by the machined inner surface of connector 16. A stern support or housing 22 for valve 18 is mounted within the tool housing 10 and is tapped to provide a centrally located hole 24 which extends part way into the housing from the upper end thereof. Hole or bore 24 functions as the housing for the spring and stem of valve 18. Disposed radially outward from centrally disposed hole 24 are a plurality of drilled passages, only two of which 26 26 are shown, which extend through housing 22. With the valve in the open position shown, the drilling fluid will pass between the seat and disc of valve 18 and will enter the interior of housing 10 via passages 26 26. Housing 22 also has, extending from its lower end, a cylindrical member 28 which, as will be explained in detail below, cooperates with piston 12 to act as a second valve. Cylindrical member 28 is centrally located with respect to the axis of housing 10 and is thus coaxial with tapped hole 24 in valve housing 22.

Proceeding down the tool housing, or right to left in FIGURE 1, a cup shaped member 32 is supported within housing 10 'by means of an internal snap ring 31. Memfber 32 in turn supports valve housing 22 which is forced down against member 32 by connector 16, connector 16 being threaded into housing 10. The lip or upper circumference of member 32 abuts valve housing 22 and member 32 is provided with a centrally located hole in the base thereof. The walls of the hole in the base of member 32 function as a guide for a reduced diameter upper portion 34 of piston 12 and cooperate with flats 36 machined in portion 34 of the piston to provide a valving action as will be described below.

Piston 12 is provided with an axial bore 38 which extends the length thereof. At the upper portion 34 of the piston, the diameter of bore 38 is slightly increased to provide an opening 40 which is commensurate in size with the cross-sectional area of valve housing extension 28. Traveling down piston 12, reduced diameter upper piston section 34 flares outwardly at shoulder 42 to an intermediate piston section `44 of increased diameter. The outer diameter of intermediate piston section 44 is equal to the internal diameter of housing 10. Intermediate piston section 44 has flats 46 in its upper portion which cooperate with the inner wall of housing 10 and a relief or enlargement 48 formed in the inner wall of housing 10 to provide a valving action which will be described below. The configuration of piston sections 34 and 44 may ybe most clearly seen from a consideration of FIGURE 6 which depicts, in cross section, the lower portion of piston section 34 having flats 36 thereof, shoulder 42 and the upper portion of piston section 44 having flats 46 thereon. Proceeding down the piston from intermediate section 44, the piston tapers at shoulder -49 to an end section 50. As will be described in more detail below, piston section 50 cooperates with an extension 52 of a movable sleeve 54 to provide additional valving action. Piston section 50 itself tapers downwardly at a shoulder 56 to form a striking end for hammer 58. As may also be seen from FIGURE 5, axial bore 38 discharges at the center of hammer 58. The striking end of hammer 58 is partially concave in shape, the reason for this shape to be d-iscussed below. The` striking surface of hammer 58, however, has sufficient area so that peening thereof is no problem.

Before discussing the chuck or work holder portion of the present invention, the operation of piston 12 as depicted by FIGURES l, 2, 5 and 6 will be described. As noted above, when drilling fluid under pressure is being delivered down the drilling string to the tool, valve 18 will remain in the open position as shown. With the piston in the down position of FIGURE l, the drilling fluid, usually compressed air, will pass between the disc and seat 20 of valve 18 and will enter the interior of housing 10 by means of passages 26 in valve housing 22. The drilling fluid will then travel downwardly through piston 12 by means of axial bore 38. The pressurized fluid which travels down axial bore 38 will be discharged from the piston and will act on the concave surface of hammer portion 58 of the piston. It should be noted that the surface area of hammer portion 58 of the piston is greater in area than that of the top of upper piston section 34 surrounding opening 40. Accordingly, the piston will begin to move upwardly or, considering FIGURE l, to the right. When the striking surfaces of the hammer 58 are lifted off the end of the tool, the drilling fluid will also act on shoulder 56. This increased surface area exposed to the drilling fluid further aids in the raising of piston 12. As the piston continues to move upwardly, piston section 50 will clear the upper end of sleeve extension 52. This condition is shown in FIGURE 2. Prior to the time that piston section 50 clears sleeve extension 52, cylindrical valve housing extension 28 will slide into opening 40 in upper piston section 32. This prevents the delivery of additional drilling fluid via passageway 28 to the bottom of the piston. When the piston has cleared sleeve extension 52, the drilling fluid which has caused the raising of the piston to the position shown in FIGURE 2 will be vented through the tool via passageways 60 (see FIG- URE 5) between sleeve extension 52 and housing 10, holes 62-62 in the sleeve passageway 64 between the tool and sleeve and holes 66-66 and bore 68 in the tool itself.

The tool will now be in the fully raised position of FIG- URE 2 and the actuating fluid which has caused the raising of the piston will have been vented. The drilling fluid now acts on the exposed upper surfaces of the piston to cause it to move rapidly downward and deliver a blow to the end of the tool. The reaction areas upon which the drilling fluid acts during the down stroke are the upper surfaces of upper piston section 34 around the periphery of opening 40 therein and shoulder 42 where piston section 34 flares outwardly to join intermediate piston section 44. It is to be noted that the drilling fluid may not pass into the interior of housing 10 in the region of piston section 50 since flats 46 on piston section 44 are above the top of relief 48 in the wall of housing 10 when the down stroke begins (the fully raised position of FIG- URE 2).

When the piston, under the action of the drilling Huid, returns to the position of FIGURE l thus striking the tool, the iiuid which has caused the down stroke will be vented through the tool by means of passing downwardly between the wall of housing and the fiats 46 on portion section 44, into relief 48 in the wall of housing 10 and then out through the tool via aforementioned passageways 60', holes 62, passageway 64 and holes 66 and bore 68. At the end of the down stroke, cylindrical member 28 is again removed from opening 40 in upper piston section 36, the fluid flow path to the interior of housing 10 between the housing and piston section 34 is closed by virtue of the flats 36 on piston section 34 being down the bore to a point where the interior of the housing is sealed through the cooperation of piston section 34 and the walls of the hole in member 32. Similarly, the vent path at the base of the piston is sealed through the cooperation of piston section 50 and sleeve extension 52. Accordingly, another up stroke will begin.

The chuck portion of the tool of the present invention comprises sleeve 54 which has the aforementioned extension 52 extending upwardly to form a first end thereof. Sleeve 54 is internally threaded at its other end so as to enable the insertion of the tool or drill 70 therein. As may best be seen from FIGURE 4, sleeve 54 is splined to a chuck 74, the splines being indicated at 76. As may be seen from FIGURES 1 and 3, the threaded joint -between the tool 70 and sleeve 54 is outside the path of direct energy transfer between the piston and tool.

It should be noted that sleeve 54 is slidably mounted within housing 10. Sleeve 54 has a portion of increased outer diameter which denes a shoulder. When the drilling string is lifted, as would be done when it is desired to blow the hole, sleeve 54, drill 70 and the piston 12 will slide downwardly to the position shown in FIGURE 3 with the shoulder on sleeve 54 in engagement with the upper end of chuck 74. In this position the piston 12 (actually hammer portion S8) will be resting on top of the tool 70 and drilling fluid will be delivered into the bore hole being drilled via open valve 18, passages 26 in valve housing 22, through the hole in member 32 (since upper section 36 of the piston will have dropped below member 32), past piston section 44 via relief 48 in the wall of housing 10, through passageways 60, through holes 62 in sleeve extension 52, passageway 64 and out through holes 66 and 68 in the tool. Under these conditions the passageway 60 and holes 62 remain open because sleeve S4, which defines passageways 60, slides within housing 10.

The above-described chuck or drill holding portion of the tool of the present invention is much less susceptible to failure than prior art devices designed for like usage. This increased reliability results from the increased number of splines in the sleeve-chuck connection permitted by the present invention and from the moving of the threaded joint between the tool and sleeve outside of the energy transfer path between the piston and work. The increase in the number of splines also increases the resistance to torque of the present invention. If, due to adverse drilling conditions, extreme torque must be applied, one or more of the mating splines may become worn in such a manner that it is no longer true and square. This can occur even with the present invention although it is much more likely to occur with prior art tools. A damaged spline will, of course, damage all parts with which it mates. In the prior art, where splined connections were employed, the splines were typically on the anvil portion of the drill. Thus, in order to prevent damage to the chuck, it was often necessary to scrap a drill before the drilling structure had worn out because of spline damage. In the present invention, because the splines are on Sleeve 54 which threadably engages the drill 70, when spline wear occurs, either or both sleeve 54 and chuck 74 may be easily replaced and without scraping of the expensive rock drill 70.

While a preferred embodiment has been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

What is claimed is:

1. A- pneumatic tool comprising:

a hollow housing;

means for delivering a pressurized drilling uid to the interior of said housing;

a differential piston disposed within said housing, said piston having a lower portion, an intermediate portion and an upper portion, said piston further having a longitudinal passage extending between the ends of said upper and lower portions whereby drilling fluid may be delivered to and will thus act upon the end of said lower portion to cause said piston to move within said housing in a first direction, said intermediate piston portion comprising:

a first piston section disposed between said upper and lower portions, said first section having a cross-sectional area greater than that of said upper and lower portions and cooperating with the interior walls of said housing to perform a valving action for venting the region surrounding said upper piston section at the beginning of movements in the first direction and for preventing communication between said regions surrounding said upper and lower pist-on sections exterior of said piston at the beginning of movements in the second direction;

means disposed within said housing above said piston and cooperating with said piston upper portion for sealing the end yof said longitudinal passage when said piston reaches its limit of movement in the lirst direction;

a drill supported from said housing below said piston, said drill having an anvil end and a work contacting end; and

means disposed in said housing and cooperating with the lower end of said piston for defining a path for venting drilling fluid from the region surrounding the end of said lower piston portion when said piston reaches its limit of movement in the first direction whereby said piston may move in a second direction opposite to said first direction under the influence of drilling fluid on the end of said upper piston portion and said end of said lower portion will deliver a blow to the anvil end of said drill.

2. The apparatus of claim 1 wherein said lower piston portion comprises:

a striking end which communicates with said longitudinal passage, said striking end being partly concave surrounding the end of said passage to define a reaction surface for drilling fluid delivered thereto through said passage.

3. The apparatus of claim 1 wherein said means for defining a path for venting drilling fluid from about the lower end of said piston comprises:

sleeve means mounted within said housing and extending upwardly from the anvil end of said drill, said sleeve means defining a plurality of vent passages between itself and the inner wall of said housing.

4. The apparatus of claim 1 wherein said drill comprises:

a work contacting portion, said work Contacting portion having an axial passage therethrough;

an anvil portion; and

a shank portion extending between said work contacting and anvil portions, said shank portion having an axial passage therein aligned with the passage in said work contacting portion, and having a plurality of passages communicating between its outer surface and the axial passage, said shank portion further having a first Section including said plurality of passages with a cross-sectional area commensurate with that of the end of the lower piston portion and a second section of increased cross-sectional area, said drill being mounted from said housing by means of said second section of said shank portion.

5. The apparatus of claim 4 wherein said lower piston portion comprises:

a striking end 'which communicates with said longitudinal passage, said striking end being partly concave surrounding the end of said passage to define a reaction surface for drilling lfluid delivered thereto through said passage.

6. The apparatus of claim 4 wherein said means for defining a path for venting drilling fluid from about the lower end of said piston comprises:

a sleeve mounted within said housing and extending upwardly past the anvil portion of said drill, said sleeve defining a plurality of vent passages between itself and the interior wall of said housing, said sleeve having an inner diameter greater than the outer diameter of said first section of said shank portion of said drill thereby defining a space between said shank portion and sleeve, said sleeve further being apertured whereby drilling fiuid may pass from said plurality of vent passages to the passages in said shank portion of said drill and thence into the hole being drilled.

7. The apparatus of claim 6 wherein said sleeve further comprises:

means threadably engaging said second section of said shank portion of said drill, said threaded connection being outside of the path of energy transfer between the anvil portion of the drill and the work.

8. The apparatus of claim 7 further comprising:

chuck means extending between said sleeve and said housing, said chuck means being splined to said sleeve.

'9. The apparatus of claim 7 wherein said sleeve is slidable longitudinally of said housing.

10. The apparatus of claim 8 wherein said sleeve is slidable longitudinally of said housing.

11. The apparatus of claim 10 wherein said lower piston portion comprises:

a striking end which communicates with said longitudinal passage, said striking end being partly concave surrounding the end of said passage to define a reaction surface for drilling fiuid delivered thereto through said passage.

12. The apparatus of claim 1 further comprising:

valving means mounted within said housing adjacent to said means for sealing the end of said longitudinal passage, said valving means -having an aperture therein commensurate in size and shape with the crosssection of said upper piston portion, the walls of the aperture in said valving means cooperating with said upper piston portion to prevent drilling fluid from entering the area surrounding said upper piston portion at the beginning of movements in the first direction.

13. The apparatus of claim 12 wherein said upper piston portion comprises:

an upper section of circular cross-section; and

a lower section having portions with the same radius as said upper section and having a plurality of portions having a reduced radius, said portions of reduced radius defining flats which cooperate with said wall of the aperture in said valving means to permit drilling uid to act on said intermediate piston portion at the beginning of movements in the second direction.

14. The apparatus of claim 13 wherein said lower piston portion comprises:

a striking end which communicates with said longitudinal passage, said striking end being partly concave surrounding the end of said passage to define a reaction surface for drilling uid delivered thereto through said passage.

1S. A pneumatic tool comprising:

a lhollow housing;

means for delivering a pressurized drilling fiuid to the interior of said housing;

a differential piston disposed within said housing, said piston having a lower portion, an intermediate portion and an upper portion, said piston further having a longitudinal passage extending between the end of said upper and lower portions whereby drilling fluid may be delivered to and will thus act upon the end of said lower portion to cause a piston to move within said housing in a first direction;

means disposed within said housing above said piston and cooperating with said piston upper portion for sealing the end of said longitudinal passage when said piston reaches its limit of movement in the first direction;

a drill supported from said housing below said piston,

said drill comprising:

a-work contacting portion, said work contacting portion having an axial passage therethrough;

an anvil portion; and

a shank portion extending between said Work contacting and anvil portions, said shank portion having an axial passage therein aligned with the passage in said work contact portion, said shank portion further having a plurality of passages communicating between its outer surface and the axial passage, said shank portion also having a rst section including said plurality of passages with a cross-sectional area commensurate with that of the end of said lower piston portion and a second section of increased cross-sectional area, said drill being mounted from said housing by means of said second section of said shank portion; and

means disposed in said housing and cooperating with the lower end of said piston and said passages in said drill for defining a path for venting drilling fluid cfrom the region surrounding the end of said lower piston portion when said piston reaches its limit of movement in the first direction whereby said piston may move in a second direction opposite to said first direction under the influence of drilling uid on the end of said upper piston portion and said end of said lower portion will deliver a blow to the anvil portion of said drill.

References Cited UNITED STATES PATENTS 2,859,733 11/1958 Bassinger et al. 173-73 2,979,033 4/ 1961 Bassinger 173-73 3,101,796 8/1963 Stall et al. 173--136 3,132,704 4/1964 Bassinger et al. 173-73 JAMES A. LEPPINK, Primary Examiner U.S. Cl. X.R. 173-136, 138 

